6 DMA CONTROLLER (DMAC)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
6-5
(Rev. 2.00)
If the arbitration cycle setting value is larger than the number of successive data transfers, successive data trans-
fers will not be suspended.
n_minus_1
Set the number of DMA transfers to be executed successively.
Number of successive transfers (N) = n_m 1
When the set number of successive transfers has completed, a transfer completion interrupt occurs.
cycle_ctrl
Set the DMA transfer mode. For detailed information on each transfer mode, refer to Section 6.5, “DMA Trans-
fer Mode.”
Table 6.4.3.5 DMA Transfer Mode
cycle_ctrl
DMA transfer mode
0x7
Peripheral scatter-gather transfer
(for alternate data structure)
0x6
Peripheral scatter-gather transfer
(for primary data structure)
0x5
Memory scatter-gather transfer
(for alternate data structure)
0x4
Memory scatter-gather transfer
(for primary data structure)
0x3
Ping-pong transfer
0x2
Auto-request transfer
0x1
Basic transfer
0x0
Stop
6.5 DMA Transfer Mode
6.5.1 Basic Transfer
This is the basic DMA transfer mode. In this mode, DMA transfer starts when a DMA transfer request from a pe-
ripheral circuit or a software DMA request is issued, and it continues until it is completed for the set number of suc-
cessive transfers or it is suspended at the arbitration cycle. To resume the DMA transfer suspended at the arbitration
cycle, a DMA transfer request must be reissued.
When the set number of successive transfers has completed, a transfer completion interrupt occurs.
DMA transfer 1 DMA transfer 2
DMA transfer request
DMA transfer
operation
DMACENDIF.ENDIFn
DMA transfer 3 DMA transfer 4
DMA transfer request
DMA transfer 7 DMA transfer 8
DMA transfer request
Figure 6.5.1.1 Basic Transfer Operation Example (N = 8, 2
R
= 2)
6.5.2 Auto-Request Transfer
Similar to the basic transfer, DMA transfer starts when a DMA transfer request from a peripheral circuit or a soft-
ware DMA request is issued, and it continues until it is completed for the set number of successive transfers or it is
suspended at the arbitration cycle. The DMAC resumes the DMA transfer suspended at the arbitration cycle with-
out a DMA transfer request being reissued.
When the set number of successive transfers has completed, a transfer completion interrupt occurs.
DMA transfer 1 DMA transfer 2
DMA transfer request
DMA transfer
operation
DMACENDIF.ENDIFn
DMA transfer 3 DMA transfer 4
DMA transfer 7 DMA transfer 8
Figure 6.5.2.1 Auto-Request Transfer Operation Example (N = 8, 2
R
= 2)